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There is a limited amount of research on the effect of obesity on persons involved in personal injury litigation. In this Blog, we will discuss the following.
- Obesity as a preexisting condition
- Comorbidities associated with obesity
- The effect of obesity on musculoskeletal disease and pain
- Osteoarthritis
- Intervertebral disc degeneration, sciatic, and lumbar radicular pain
- Low back pain
- Chronic pain
- Obesity and blunt trauma secondary to mechanical falls and motor vehicle accidents
- Effect of obesity on functional recovery in trauma patients
- Obesity treatment: conservative and medication management
- The role of bariatric surgery as related to injury and subsequent treatment
- If treatment for obesity improves chronic pain conditions
- Obesity treatment as a compensable consequence of injury
Obesity as a preexisting condition
The American Medical Association designated obesity as a disease in 2013. The majority of current research on obesity uses an outcome measure of body mass index (BMI). This is calculated by dividing height in kilograms by weight in meters squared (kg/m2). The Centers for Disease Control and Prevention (CDC) have defined the following categories of obesity.
Obesity Categories[1]
| BMI in kg/m2 | Weight Status |
| Below 18.5 | Underweight |
| 18.5-24.9 | Normal or Healthy weight |
| 25.0 -29.9 | Overweight |
| 30.0-34.9 | Class 1 obesity |
| 35-39.9 | Class 2 obesity |
| 40 or higher | Class 3 or Severe obesity |
Any value over 30 kg/m2 is considered in an obese category, and severe obesity is defined as a BMI of 40 kg/m2 or greater. The percentage of the U.S. population in the categories of obese and severely obese both increased by over 30% (age-adjusted) from 2000 to 2018. In 2018, 42.4% of the population was obese, and 9.2% of the population was severely obese. Severe obesity is highest among adults aged 40-59 years.[2] An additional way to measure obesity is waist circumference. A value of greater than or equal 40 inches in men and 35 inches in women is considered elevated and indicates increased risk of cardiometabolic disease such as type 2 diabetes, hypertension dyslipidemia, heart disease, and fatty liver disease.
People become obese due to multiple factors, including genetics, ethnicity, lower socioeconomic status, sedentary lifestyle, diet, sleep deprivation, smoking status, presence of some endocrine disease (e.g. diabetes and thyroid disease), and use of certain medications (e.g. antipsychotics, tricyclic antidepressants, some anti-epilepsy drugs, and some diabetes drugs).
Comorbidities associated with obesity
Obesity is associated with significant increases in morbidity and mortality. Obesity has surpassed smoking as the number one cause of preventable disease and disability. A BMI greater than 25.0 kg/m2 (overweight category or higher) is associated with increased risk for chronic health conditions, poor health-related quality of life, and increased risk of premature death.[3] Diseases associated with obesity include coronary heart disease, diabetes mellitus, dyslipidemia; hypertension, stroke, venous thrombus, depression, chronic kidney disease, and cancer (e.g. liver, kidney, breast, endometrial, prostate, and colon).[4]
Effect of obesity on musculoskeletal disease and pain
Obesity is associated with several types of musculoskeletal pathology.
Osteoarthritis: The most significant impact of obesity on the musculoskeletal system is associated with osteoarthritis.[5], [6] Increased body weight adds pressure to weight-bearing joints, alters biomechanical patterns, and releases inflammatory-causing proteins. This latter effect can occur in all joints, including those that are non-weight-bearing, such as the hand, and is proposed to increase the risk of developing osteoarthritis. Obesity also increases the risk of osteoarthritis in more than one joint, increases the severity of the disease, increases complications, and can cause poorer outcomes after surgery. [7]
Chronic pain: Chronic pain appears to be associated with abdominal obesity, but the mechanism of this association has not been elucidated. Metabolic derangement may predispose to pain, but there may also be a bidirectional mechanism, in that chronic pain may lead to decreased physical activity, depression, and obesity. Obesity is associated with higher rates of opioid use, with the largest self-reported reasons for use including back pain, joint pain, and muscle/nerve pain.[8] The potential benefits of weight loss as a strategy for reducing or preventing chronic pain have yet to be demonstrated.[9]
Low back pain: There appears to be a high prevalence of overweight/obesity among individuals with musculoskeletal disorder diagnoses such as low back pain; most markedly in those who also have osteoarthritis, but there is insufficient evidence to make a recommendation for or against obesity as a prognostic factor for the conversion from acute to chronic low back pain.[10] Fat mass and location of deposition appear to have some effect on this, with greater symptoms present in individuals with fat distributed mostly around the trunk/abdomen. This may be due to mechanical loading of body mass but may also be due to systemic or metabolic processes, such as that related to inflammatory-causing proteins described above.[11]
Intervertebral disc degeneration, sciatica, and lumbar radicular pain: Research is conflicting in terms of an association of elevated BMI (in particular overweight or obese) and development of intervertebral disc degeneration, with the hypothesis that this is due to mechanical overload of the spinal segments.[12] There does appear to be an association with lumbar radicular pain and physician-diagnosed sciatica. The mechanism is not clearly elucidated and may also be related to inflammation. [13]
Obesity and blunt trauma secondary to mechanical falls and motor vehicle accidents (MVAs)
Obesity appears to be associated with increased probability of sustaining a workplace injury, but the direct contribution of obesity, including the mechanism of how excessive body weight relates to occupational injury and/or how obesity interacts with other occupational hazards has not been established.[14] Obesity also appears to worsen outcomes after blunt trauma secondary to mechanical falls or motor vehicle accidents in an adult population. Outcomes may not be as much related to the injury, as to medical comorbidities which complicate recovery. There was an approximate 300% increase in mortality from mechanical falls and a 350% increase from MVAs in obese patients versus non-obese patients in a study with data from 2004 to 2012. Increased BMI may increase the Injury Severity Score, with more severe outcomes, including higher fracture rates.[15] In a systematic review/meta-analysis, there was a 23% overall complication rate post-operatively in orthopedic trauma patients with a BMI greater than 30 kg/m2 versus a 14% rate in the group with BMI less than this. [16]At least part of increased morbidity and mortality is thought to be related to elevated inflammatory markers.
Effect of obesity on functional recovery in trauma patients
Functional recovery in obese patients is often delayed when compared to the time to recovery in non-obese patients. This delay is directly correlated with the severity of obesity. [17] The recovery in obese patients may also be of lesser magnitude and rate than in those who are not obese.[18]
Obesity treatment: conservative and medication management
The “U.S. Preventive Services Task Force Draft Recommendations” recommends individuals with a BMI of 30 to 24.9 kg/ m2, or individuals with a BMI of 25 to 29.9 kg/m2 with risk factors for coronary vascular disease (diabetes, hypertension, or dyslipidemia) receive intensive, multicomponent behavioral intervention or behavior-based weight loss maintenance interventions.[19] For individuals with a BMI of 35 kg/m2 or greater, more aggressive treatment options are recommended, including pharmacologic therapy, or bariatric surgery.
Multicomponent behavioral intervention programs commonly include group sessions (12 or more in the first year) to help the person make healthy eating choices to encourage physical activity, and to monitor weight.[20]
There are multiple drugs available for obesity treatment. If pharmacological therapy is chosen as a treatment, the first step is to optimize medications for comorbid disease states (such as diabetes, depression, or autoimmune disease) with medications not known to produce weight gain. The choice of an anti-obesity drug depends on an individual’s comorbidities, patient preference, potential adverse effects, and the relative contraindications. Generally, if a patient has not lost 4 to 5 percent of body weight after 12 weeks of therapy, the drug therapy should not be continued. There is little evidence a different anti-obesity drug will have better results.
The role of bariatric surgery as related to injury and subsequent treatment
General indications for bariatric surgery include an BMI greater than 35 kg/m2 with at least one obesity-related comorbidity (e.g. hypertension, diabetes, nonalcoholic fatty liver disease, debilitating arthritis, and/or venous stasis disease), or a BMI of 40 kg/m2 or greater (with or without comorbidities).[21] While individuals who qualify for this surgery continue to have more pain following their obesity related surgery than the general U.S. population, severely obese individuals who undergo bariatric surgery have reduced pain (by approximately 60 %) and improved physical function (by approximately 75%). [22]
The benefits of surgery appear to decrease between years 1 and 3, and medication usage for pain has a corresponding increase.4 Clinically significant improvements in osteoarthritis symptoms also appear to decrease over this same period.4 It appear overall deterioration in improvement continues, with the longest current follow up study showing this at 6 years.[23] Longer-term studies with better methodologic designs are needed to evaluate the role of bariatric surgery as a primary treatment for musculoskeletal pathology, and particularly for low back symptoms.[24]
Bariatric surgery has been suggested before elective spinal surgery. In one study on posterior lumbar fusion, the obesity procedure decreased the risk of medical complications and infection when compared to severely obese patients who did not undergo bariatric surgery. When compared to non-obese patients, those who had undergone bariatric surgery still had higher rate of infection, reoperation, and readmission.[25]
There is also research showing massive weight loss (greater than 10% of total body weight) within 6 months before is associated with higher rates of postoperative complications after fusion surgery compared to patients without such weight loss.[26] It is of note, no study evaluates the overall outcome of spinal fusion in terms of pain and function comparing a group with bariatric surgery versus those without in patients who qualify for the latter procedure. In a somewhat conflicting presentation using retrospective data, bariatric surgery before total joint arthroplasty is associated with a greater 90-day postoperative complication rate and higher immediate hospital costs when compared to obese patients without bariatric surgery.[27]
Bariatric surgery is associated with long term health effects. These are related to nutritional deficiencies, altered hormones, and bone metabolism. The consequences can include anemia, certain types of neuropathy, and /or osteoporosis. The impact of musculoskeletal health remains uncertain, with the possibility that over the long term, bariatric surgery could actually result in additional musculoskeletal pathology.
Does treatment for obesity improve chronic pain conditions
There is limited evidence showing obesity treatment improves chronic pain. Several factors complicate any study of this treatment for painful conditions.
- One issue is the lack of evidence of how obesity directly influences an injury and subsequent health effects. As noted in Part I, the exact mechanism of how obesity leads to an injury has not been elucidated, nor has that of related health effects. Some have suggested this could be related to factors such as mechanical stress or inflammation. The potential benefits of weight loss as a strategy for reducing or preventing chronic pain have yet to be demonstrated.[28]
- It can be difficult to ascertain the true pain generator in a pain patient. An example is determining whether the peripheral pain is due to a prior injury, to a comorbid condition such as diabetes-related neuropathy, or to a complication of bariatric surgery (in a patient who has undergone this procedure).
- The available research has not addressed if bariatric surgery has a positive association with pain relief for chronic pain and/or severe pain patients. In osteoarthritis patients, limited research suggests that a greater than 10% reduction in body weight induced by diet accompanied by exercise improves pain control and function. Participants had mild-to-moderate arthritis and did not have severe pain.[29] In another study of patients with low-level pain who were not actively seeking pain treatment, decreased pain with weight loss was described to be a “serendipitous effect” The authors raised, but did not answer, the question of whether this same effect would be found in patients with chronic pain.[30]
- The severity of obesity is also an issue because what applies to a severely obese patient in terms of treatment may not apply to a less obese one.[31]
Obesity treatment as a compensable consequence of injury
Sometimes plaintiffs in personal injury cases claim obesity is a compensable consequence of an injury (i.e. when an individual gains weight due to lack of exercise or a medication prescribed to them during recovery). Any attempt to make such a claim will require a detailed presentation, which includes specific pre-injury weight, an examination of variables other than those related to the injury (such as preexisting medical pathology and treatment), and evidence of weight increase status post the injury and/or treatment. Counter arguments for such claims will be the substantial evidence of incidence of increased weight with age in the general population, and lack of evidence that using obesity treatment is effective as a therapy for chronic pain.
In patients with preexisting obesity, acute treatment and initial rehabilitation after an injury may be more complicated, require a longer duration, and be more costly than in individuals who are not obese. When recommending future treatment, an issue is the lack of evidence of sustained duration of obesity interventions, and evidence that obesity treatment will either prevent the development of chronic pain or actually address this. Again, any proposed weight-loss interventions must be considered case-by-case.
Summary
Obesity is on the increase, with over 40% of the population with this diagnosis using a BMI measure, and is now the number one cause of preventable disease and disability. Obesity appears to affect multiple musculoskeletal conditions due to not only mechanical changes induced by increased body habitus, but also as related to inflammation. Outcomes appear worsened in obese patients with injury, including for those undergoing surgery, with substantial increases in mortality noted in specific cases of mechanical falls and motor vehicle accidents.
At a minimum, there should be awareness of the impact of this condition on personal injury cases, in terms of initial treatment, and postoperative sequelae. The direct contribution of obesity alone, versus other factors that contribute to morbidity and mortality, remains to be determined.
We hope this blog helps to illuminate the complexities of obesity in personal injury cases. Questions remain as to (1) how an obese state contributes mechanistically to injury; (2) what are the mechanisms by which obesity contributes to chronic pain; (3) does a state of obesity contribute to a conversion from acute to chronic pain; and (4) will treatment of obesity improve chronic pain states. In litigation in which the plaintiff’s obesity is an issue, and in particular in terms of treatment, the questions must be answered case-by-case because there is insufficient knowledge to support general statement of cause and effect.
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[2] Available at: https://www.cdc.gov/nchs/products/databriefs/db360.htm. Accessed 8/8/2020.
[3] Jia H, et al. Population-Based Estimates of Decreases in Quality-Adjusted Life Expectancy Associated with Unhealthy Body Mass Index. Public Health Rep. 2016 Jan-Feb;131(1):177-84.
[4] Grover SA, et al. Years of life lost and healthy life-years lost from diabetes and cardiovascular disease in overweight and obese people: a modelling study. Lancet Diabetes Endocrinol. 2015;3(2):114.
[5] King LK, et al. Obesity & osteoarthritis. Indian J Med Res. 2013;138(2):185-93.
[6] Blagojevic, M, et al. Risk factors for onset of osteoarthritis of the knee in older adults: a systematic review and meta-analysis. Osteoarthritis Cartilage 2010; 18(1): 24–33.
[7] Brady SRE, et al. High baseline fat mass, but not lean tissue mass, is associated with high intensity low back pain and disability in community-based adults. Arthritis Res Ther. 2019 Jul 5;21(1):165.
[8] Poudel D, et al. The Impact of Obesity on Disease Activity and Treatment Response in Rheumatoid Arthritis. Rheumatol Rep. 2020 Aug 1;22(9):56.
[9] Ray L, et al. Mechanisms of association between obesity and chronic pain in the elderly. Pain. 2011. PMID: 20926190
[10] Kreiner DS. Guideline summary review: an evidence-based clinical guideline for the diagnosis and treatment of low back pain. Spine J. 2020 Jul;20(7):998-1024
[11] Brady SRE, et al. High baseline fat mass, but not lean tissue mass, is associated with high intensity low back pain and disability in community-based adults. Arthritis Res Ther. 2019 Jul 5;21(1):165.
[12] Cannata F, et al. Intervertebral disc degeneration: A focus on obesity and type 2 diabetes. Diabetes Metab Res Rev. 2020;36(1): e3224. doi:10.1002/dmrr.3224
[13] Shiri R. et al. Obesity as a risk factor for sciatica: a meta-analysis. Am. J. Epidemiol. 2014. 179:929-37.
[14] Lin TC, et al. Does obesity contribute to non-fatal occupational injury? Evidence from the National Longitudinal Survey of Youth. Scand J Work Environ Health. 2013;39(3):268-275.
[15] Barry R. et al., 2019. The impact of BMI on adult blunt trauma outcomes. Am. Surg. 85;1254-62.
[16] Kinder F, et al. The Effect of an Abnormal BMI on Orthopaedic Trauma Patients: A Systematic Review and Meta-Analysis. J Clin Med. 2020 May 1;9(5):1302
[17] Dhungel V, et al. Obesity delays functional recovery in trauma patients. J Surg Res. 2015 Jan;193(1):415-20
[18] Vincent HK, et al. Effects of obesity on rehabilitation outcomes after orthopedic trauma. Am J Phys Med Rehabil. 2012 Dec;91(12):1051-9
[19] US Preventive Services Task Force, et al. Behavioral Weight Loss Interventions to Prevent Obesity-Related Morbidity and Mortality in Adults: US Preventive Services Task Force Recommendation Statement. JAMA. 2018;320(11):1163.
[20] Available at: https://www.aafp.org/news/health-of-the-public/20180221uspstfobesity.html. Accessed 8/22/2020.
[21] Pentin PL, Nashelsky J. What are the indications for bariatric surgery? J Fam Pract. 2005;54:633–634
[22] King WC, et al. Change in Pain and Physical Function Following Bariatric Surgery for Severe Obesity. JAMA. 2016. PMID: 27046364
[23] Peltonen M, et al. Musculoskeletal pain in the obese: a comparison with a general population and long-term changes after conventional and surgical obesity treatment. Pain. 2003;104(3):549–557.
[24] Joaquim AF, et al. Bariatric Surgery and Low Back Pain: A Systematic Literature Review. Global Spine J. 2020 Feb;10(1):102-110.
[25] Jain D, et al. Bariatric surgery before elective posterior lumbar fusion is associated with reduced medical complications and infection. Spine J. 2018.
[26] Rudy HL, et al. Rapid Bodyweight Reduction before Lumbar Fusion Surgery Increased Postoperative Complications. Asian Spine J. 2020
[27] Liu JX, et al. Preoperative Bariatric Surgery Utilization Is Associated With Increased 90-day Postoperative Complication Rates After Total Joint Arthroplasty. J Am Acad Orthop Surg. 2020.
[28] Ray L, et al. Mechanisms of association between obesity and chronic pain in the elderly. Pain. 2011. PMID: 20926190
[29] Messier SP, et al. Effects of intensive diet and exercise on knee joint loads, inflammation, and clinical outcomes among overweight and obese adults with knee osteoarthritis: the IDEA randomized clinical trial. Jama. 2013;310:1263–1273.
[30] Schrepf A, et al. Improvement in the Spatial Distribution of Pain, Somatic Symptoms, and Depression After a Weight Loss Intervention. J Pain. 2017 Dec;18(12):1542-1550.
[31] Joaquim AF, et al. Bariatric Surgery and Low Back Pain: A Systematic Literature Review. Global Spine J. 2020 Feb;10(1):102-110.